Viscosity, pretreatment techniques

Flow techniques are particularly suitable for monitoring environmental parameters in waters. Moreover, flow methods offer unique possibilities for automatic sample pretreatment, involving inline dilution or filtration, adjustment of viscosity, ionic strength, or pH as well as removal of solid and colloidal matrix constituents via in-line dialysis separation techniques. 

Analytical advantages of the ICPAES technique are the simultaneous or sequential multielement capability, a relative absence of matrix interference, high precision, simplicity of calibration, and a wide dynamic range. Commonly employed pretreatments include dry ashing, acid extraction, wet mineralization, and the use of PPRs. Wet digestion is preferable for pretreatment of most biological material, with the exception of serum or plasma. Pretreatment with PPRs is the preferred method for plasma and serum samples. This then leaves only the metals in solution for analysis by ICPAES. Excellent results are obtained using the Mg emission line 279.553 nm [96]. Inconsistencies with this type of analysis are usually due to aerosol production and introduction into the plasma. It is also important that the viscosity and surface tension of the samples and standards match. 

Crude oil is a complex matrix of varying viscosities and mixed phases (organic, water and particulate matter) and therefore not an ideal matrix for analysis. The determination of the metals in crude oil requires pretreatment to the sample before presentation to the instrument. This is the stage where most of the errors occur and is time consuming. The selection of a particular procedure depends upon (1) analytical technique to be employed, (2) nature and the number of the samples to be analyzed, (3) desired degree of precision and... 

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